Kent County Council has revealed the evidence for its decision to make permanent the closure of one arm of a key junction – and it is pretty convincing.

This week, cabinet member Neil Baker (Con) announced the closure of Cranborne Avenue’s junction with the Loose Road at the Wheatsheaf junction in Maidstone would be made permanent at the expiry of an 18-month trial period next week.

The decision upset many motorists from the Shepway side of the junction who say they now face longer journeys and delays getting into the town centre.

But KCC has now published the report by consulting engineers Charles and Associates from East Malling on which the decision was based.

The company carried out traffic surveys during the morning peak period, regarded as between 7am and 10am, and the evening peak period, 4pm to 7pm, both before the closure (in September 2021) and afterwards (in June 2022).

Cranborne Avenue had formed one arm of a four-way junction at the Wheatsheaf controlled by traffic lights and its closure enabled the other three lanes to stay green for longer.

The consultants found the total traffic throughput at the Wheatsheaf junction during weekday peak periods in both 2021 and 2022 was almost identical.

They also surveyed traffic at the Plains Avenue junction with Loose Road where it was said that Cranborne Avenue traffic was now being diverted.

They did find there had been “a slight increase” of circa 3-5% in traffic throughput at the junction – from an hourly peak of 2,453 vehicles pre-closure in the morning, to 2,575 after, and from an hourly peak in the evening of 2,663 pre-closure to 2,753 after.

However, the consultants also measured the average length of traffic queues in metres at each of the junction arms over half-hourly periods at both the Wheatsheaf and Plains Avenue.

They found “a significant decrease in average queue lengths” at the Wheatsheaf junction following the closure of Cranborne Avenue.

During the AM peak period, there had been a reduction in total average queue lengths of 1,522 metres (53%).

In the evening, the reduction was 817 metres (42%).

The most significant reductions in queues were on the Loose Road North arm in the mornings and on the Sutton Road arm in the evenings.

However, the reductions were not universal.

The figures showed the average queue length on the Loose Road South arm actually increased in the evenings from 585 metres to 633 metres. The consultants did not offer any explanation for this aberration.

They also found that despite a slight increase in total traffic movements at Plains Avenue, there has been a decrease in average queue lengths at the junction following the closure of Cranborne Avenue.

The average queue length in the morning peak had dropped from 72 metres to 26 metres and in the evening it had dropped from 60 metres to 22 metres.

The engineers also looked at whether there had been an increase in the number of accidents at either junction, as residents have frequently claimed that exiting Plains Avenue onto Loose Road, where there is no traffic light control, is dangerous.

The consultants found no significant changes in the number of accidents at either junction.

The consultants also carried out three “spot checks” on Plains Avenue since the closure and found a maximum queue length of only seven vehicles which they described as “minimal.”

Their report said: “The observed traffic data collected before and after the closure of Cranborne Avenue strongly indicates that the closure has had a largely positive impact on the operation of the junction without having a significant detrimental impact elsewhere on the network.

“In particular, the A229 and A274 approaches to the junction have observed significant reductions in queues which would in turn reduce driver delay and improve journey time reliability on the corridor.

“Furthermore, a reduction in queueing vehicles would also help to reduce air quality impacts in this area.”

They also concluded the closure of Cranborne Avenue had “not had a detrimental impact in terms of additional queues and delays elsewhere.”

KCC’s Highways said that following the decision to make the closure permanent it was instructing its maintenance contractor, Amey, to implement the necessary measures and to remove the temporary barriers and signage.

The consultants’ full report can be viewed here.

There was no explanation why it has not been published until now, given that their last survey was in June of last year.

Ahead of the temporary closure order for Cranborne Avenue, highways officers had predicted it would save 17 seconds on the average journey time.

Charles and Associates, although identifying shorter queues, did not attempt to put a figure on any time savings achieved.